On forage harvesters, in particular, but also on combines, removable front harvesting attachments are being applied for the harvesting and recovery of crop, which are mechanically relatively costly and heavy. Such front harvesting attachments are, in particular, so-called corn pickers or corn mower-choppers. At present an ever greater effective width of the front harvesting attachments is desired for reasons of economy, in order to be able to harvest a field in shorter time and with fewer passes. A usual commercially available width is, for example, 6 m. Due to the great weight of the wider front harvesting attachments, known forage harvesters equipped with driven front wheels and steerable rear wheels that must perform at high power and therefore also exhibit great weight, in order to be able to operate together with the wide front harvesting attachments but nevertheless exceed the legally permitted axle load values on the front axle. In order to be able to apply such wide front harvesting attachments with the known two axle design, a completely new design concept would be required for a forage harvester. Similar problems can also occur with combines.
It is known to provide supporting wheels on relatively light weight pick-up devices. For example, EP-386 430-B1 reveals a crop intake arrangement for harvesting machines, a so-called pick-up with a take up drum, which is supported by wheels suspended on a full floating axle or walking beam attached by a pivotal connection; U.S. Pat. No. 4,463,546 shows a similar take up arrangement provided with support wheels, that is mounted on a combine and is used to take up grain crops previously cut and lying on the ground; and De-197 26 917-A shows a forage harvester with a pick-up also supported on wheels.
The problem underlying the invention is seen in the high axle loads of two-axle agricultural vehicles equipped with relatively wide and heavy attached implements.